This invention relates to valves for controlling the flow of a liquid wherein the valve passes a predetermined quantity of liquid and then automatically closes. These valves are known alternatively as metering valves or flush valves.
Metering valves in common use are generally of two types. The first type, seen in such applications as commercially available toilets and the like, consist of providing a liquid holding chamber calibrated or sized to hold the metered quantity of a liquid, together with a float valve or other level sensing mechanism designed to detect when the chamber has been filled to the level corresponding to the quantity desired. This controls the intake of liquid to the chamber until the desired quantity of liquid is available and held within the chamber. The valve is also provided with some form of dump mechanism for dumping all, or substantially all of the fluid, from the chamber into the desired outlet. Such valving systems are simple, easily constructed and have proven highly reliable. However, they have several disadvantages; they essentially are limited to metering a substantial quantity of liquid; by their nature, since they require either an air-liquid or a dual-density liquid interface in order to trigger the standard level sensor mechanisms, they are inherently non-hermetically sealed.
A second form of metering valve typically utilizes some form of internal cylinder, or moving mechanism, which traverses from an open to a closed position by the pressure of the liquid being supplied to the valve, and the speed of which traversal is controlled by a bleed orifice. The movement of the cylinder, or mechanism, is in turn used to actuate the valve.
Typical prior art valves of this type, while they are hermetically sealed, utilize some form of sliding valve-gate or diaphragm mechanism. As the forces available within such valve mechanisms are insufficient to actuate the valve against significant differencial pressure, these valves also have the significant disadvantage that they are unable to operate against very large pressure differentials from inlet to outlet, and they are severely restricted in the ability to design in various metering rates because of physical limitations within the valve on the metering or bleed orifice sides caused by the overall mechanical arrangement of the interior of the valve body.